2. Overview of the WOL facility

The WOL service enables IT Support Staff, end-users and the HFS Backup Service to switch computers on remotely. The service is accessed via the OUCS registration web pages using the University Single Sign-On (webauth) login. The diagram below illustrates the main software components that constitute the WOL infrastructure:

The main steps involved in setting up a WOL service within a department or college are:

• Install FiDo software, one per subnet where wake on LAN is required.
• Register MAC addresses with the WOL service
• Change BIOS settings and possibly network card configurations to support WOL, (only necessary where the capability has been disabled).

The WOL service can be used to reduce the amount of time computers are left on unnecessarily in the following scenarios:

• The HFS backup service can use the WOL service to switch computers on just before backups are performed. Desktop computers can also be configured to switch off after the HFS backup service has finished.This means computers do not need to be left on all through the night. Using the WOL service in this way may also mean that fewer backups are missed.
• Users can switch their computer on remotely, for instance, when away at a conference. This means computers do not need to be left on just in case they are needed.
• Users can use the WOL service to switch computers their computer on automatically, for example just before they arrive for work. Computers normally take up to two minutes to boot so WOL can be used to avoid this wait. (A computer may take longer to become usable however if 'log-in scripts' need to run).

The WOL service cannot be used to reduce energy consumption in these scenarios:

• Computers are often left on overnight to preserve the 'desktop context' (the applications and web pages that are open at the end of the day). The most obvious solution in this case is to use 'hibernate' (ACPI-S4) power-saving mode. Anyone wanting to try this approach should test that hibernate mode does not negatively effect the use of other tools e.g. version control and locking with files stored on a 'shared network drive'.
• Some users receive extremely large volumes of emails so need to use email filters to organise this information. This is often achieved by configuring filters within the desktop e-mail client. Another approach would be to migrate the filters to the e-mail server.
• Some people use multiple desktop computers as a development and testing environment. It may be feasible to use virtualisation software on just one machine to emulate applications running on different operating systems.
• Some people use desktop computers as servers. It might be possible instead to use a virtual server in an efficient data centre.
• Some computers are left on overnight to perform computation experiments. Since these computers are doing useful work there is no need to consider turning them off.
• Some computers do not support WOL and may need to be left on. Departments and colleges may like to consider allowing the OxGRID service to use these computers to perform experiments. By donating this spare capacity, electrical energy that would otherwise be wasted can be put to good use.
• Some computers are used to 'keep-alive' other computers. This is an example of a practise with no easy workaround. Not all computers can be switched off overnight - in this case and possibly others, it may be necessary to conclude that some computers need to be left on.

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